mysql复杂语句

Question

问题：两个表，第一个包含userid（约束fk）和列'name'，第二个表包含两列int和id（外键），我需要的是找到max（column1-column2）和从第一个表中为其指定名称;

我在做什么： MySQL的＆GT;

select u.name, MAX(table2.column1-table2.column2) As var 
  from table1 u, table2 b 
 where u.userID(from table1) = b.userID(from table2)
   and (b.column1-b.column2) = var;

在这种情况下它表示“未知列var”，是否可以使用withoud triggers / procedures？

any1？:)

Answer 1

也许尝试子查询？

select u.name, (b.column1 - b.column2) as var 
  from table1 u, table2 b 
 where u.userID(from table1) = b.userID(from table2)
   and (b.column1-b.column2) = ( select MAX(column1 - column2) from table2);

Answer 2

我认为这是正确的解决方案：

select u.name, 
    MAX(table2.column1-table2.column2) As var 
from table1 u
    join table2 b 
        on b.userId = u.userId
where u.userID(from table1) = b.userID(from table2)
group by u.name